Machine Type Communication (MTC) User Equipment (UE) is also referred to as Machine to Machine (M2M) user communication equipment, which is a main application form of a current internet of things. Recently, due to high spectrum efficiency of a Long-Term Evolution (LTE)/LTE-Advance (LTE-A) system, more and more mobile operators select LTE/LTE-A as an evolution direction of a broadband wireless communication system. LTE/LTE-A-based MTE multi-variety data services will be more attractive.
The existing LTE/LTE-A system is used for transmission based on dynamic scheduling of each subframe, that is, each subframe may transmit different control channels.
In LTE/LTE-A, a Physical Downlink Control Channel (PDCCH) and an Enhanced Physical Downlink Control Channel (EPDCCH) are defined. Information borne by a Physical Control Format Indicator Channel (PCFICH) is used for indicating the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols for transmitting the PDCCH in a subframe. A Physical Hybrid-Automatic Repeat-reQuest (ARQ) Indicator Channel (PHICH) is used for bearing ACK/NACK feedback information of uplink transmission data. A downlink control channel adopts blind detection, and a terminal attempts to demodulate the downlink control channel with different aggregation levels and candidate sets in a certain Search Space (SS).
TABLE 1Search space Sk(L)Aggregation levelSizeNumber of PDCCHTypeL[in CCEs]candidates M(L)UE-specific16621264828162Common41648162
An existing UE-specific Search Space (USS) and Common Search Space (CSS) are as shown in Table 1 and Table 2. Table 1 is a PDCCH SS, and Table 2 is an EPDCCH SS (one distributed EPDCCH-PRB-set-Case 3).
An SS consists of candidate sets corresponding to different aggregation levels, a terminal needs to attempt to demodulate each candidate set until the candidate sets are demodulated correctly when demodulating a control channel, and otherwise, it is considered that the terminal does not receive own control channels.
TABLE 2Number of EPDCCH candidates Mp(L) for Case 3NRBXpL = 1L = 2L = 4L = 8L = 16284210445421844422
The EPDCCH is used for bearing Downlink Control Information (DCI), including uplink scheduling information, downlink scheduling information and uplink power control information.
Usually, an MTC terminal may obtain DCI by demodulating the EPDCCH at each subframe, in order to demodulate a Physical Downlink Share Channel (PDSCH) and implement scheduling indication information of a Physical Uplink Share Channel (PUSCH).
MTC application terminals are distinguished into at least two types of terminals, namely low-cost terminals called due to limited radio frequency receiving bandwidth, and coverage enhancement terminals called due to significant reduction of coverage performance caused by limited position or characteristics of the present terminal. For example, most of smart meter reading type MTC terminals are fixedly installed in a low coverage performance environment such as a basement, and are mainly used for sending packet data, a data rate is lowly required, and a large data transmission delay can be tolerated. Correct data transmission for a coverage enhancement terminal is ensured in a manner of repeated sending on a time domain. Due to limited receiving bandwidth, only the EPDCCH can be used. When DCI of a unicast service is repeatedly transmitted and scheduled, even if USS resources of all of six Physical Resource Blocks (PRB) can be occupied, the resources can be configured to different narrowband positions by means of an evolved Node B (eNB). When DCI of a common message is repeatedly transmitted and scheduled, a piece of DCI in each subframe needs to occupy all 6PRB resources of an SS, and in this case, other common messages cannot be scheduled. Therefore, it is necessary to consider one or more possible CSSs or USSs for low-cost and/or coverage enhancement MTC terminals.
Any effective solution has not been proposed yet at present for the problem in the related art about how to determine the quantity and positions of SSs for low-cost and coverage enhancement MTC terminals.